Recently, paper-based patterned solid-phase sensors (which are simple, portable, disposable and inexpensive) have been developed to run multiple bioassays and controls simultaneously.17 These portable biosensing papers are extremely useful in remote settings as well as less industrialized countries where simple bioassays are essential in the first stages of detecting disease, and for monitoring environmental and food based toxins.
Several conventional deposition techniques such as dip coating,8 spin coating,9 aerosol spraying,10 and electrophoretic deposition11 have previously been used to deposit bioactive sol-gel derived materials. Among these, dip and spin coating are not practical for large-scale production. In addition, they are time consuming and are wasteful when dealing with expensive bioreagents. Aerosol spraying can be used for deposition of biomaterials, but is not easily adaptable to formation of millimeter scale patterns or for precise control of sol gel deposits. Electrophoretic deposition is normally used for fabrication of electrodes and the process requires an electrically conductive surface.12 
It has been shown that entrapment of biomolecules within sol-gel derived materials allows proteins to retain their bioactivity for prolonged periods of time.13,14 Furthermore, sol-gel based materials have previously been shown to be amenable to ink jet deposition (although not with proteins)15 or screen printing with entrapped enzymes.16 
Ink jet printing has been used to dispense, deposit or pattern, in either 2D or 3D arrangements cells/tissue,17,18 DNA,19 antibodies,10 and enzymes.2,15,18 